Strainer and check valve assembly



Nov. 30, 1954 H. ALLAN 2,695,711

ETRAINER AND CHECK VALVE ASSEMBLY Filed May 8, 1952 474 wmgg United States Patent O STRAINER AND CHECK VALVE ASSEMBLY Hugh Allan, Memphis, Tenn., assignor to Rotary Lift Company, Memphis, Tenn., a corporation of Delaware Application May 8, 1952, Serial No. 286,796

3 Claims. (Cl. 210-166) My invention relates generally to hydraulic elevators and lifts, and more particularly to an improved one-way strainer.

One of the difliculties frequently encountered in the operation of hydraulic elevators and lifts is caused by foreign matter in the hydraulic fluid, usually oil. Such foreign matter interferes with the operation of the control valve which is opened to permit oil to escape from the jack cylinder of the lift or elevator to the reservoir. This valve necessarily has minute passageways through which the oil must flow at times, and dirt, rust, and scale may clog these passageways or lodge on the valve or its seat, interfering with proper operation of the valve. The control valve is generally of the type shown in the patent to Jaseph No. 2,355,164, issued August 8, 1944. Most of such foreign matter is in the form of rust and scales which flake from the walls of the jack cylinder and its plunger. Rusting occurs because these parts are sometimes exposed to the atmosphere for a considerable time during shipment to the place the lift or elevator is to be installed. Furthermore, the lift or elevator may not be set up and used for some time due to delays in construction of the building in which they are to be installed.

It is therefore an object of my invention to provide an improved strainer which will strain the oil as it returns from the jack cylinder, but will permit oil to bypass the strainer when it flows from the pump to the, jack cylinder.

A further object is to provide an improved strainer which is particularly adapted for use in a hydraulic system having a pipe through which the hydraulic fluid flows to and from a hydraulic elevator, lift, or motor.

Other objects will become apparent from the following description, reference being had to the accompanying drawings, in which:

Fig. 1 is a diagrammatic view of a hydraulic lift and the hydraulic circuits and parts by which its operation is controlled, portions being shown in different scales; and

Fig. 2 is a central vertical cross sectional-view of an improved strainer and shutoff cock assembly.

Referring to Fig. 1, oil is withdrawn from a reservoir through a strainer 12 by a suitably driven constant displacement pump 14. The discharge side of the pump is suitably connected to a pressure relief valve 16 which permits flow from the discharge side to the inlet side of the pump whenever a predetermined pressure is exceeded. A check valve 18 is connected to the discharge outlet of the pump and the outlet side of this check valve is connected to a T 19, one branch of which is connected to the reservoir 10 through a control valve 20 which may be of the type shown in said Patent No. 2,355,164.

A combined strainer and check valve assembly 22 is connected to the T 19 by a pipe 23, and is connected to the lower end of a jack cylinder 24 by a pipe 25. A plunger or jack 26 is reciprocable in the cylinder 24, and is adapted to elevate and lower a load 28.

The assembly 22 comprises a body 30 which is provided with a bore 32 for a shutoff cock 34, the latter a polygonal end portion 36 for engagement with a wrench. Formed integrally with the body 30 is an internal wall 38 having openings 40 and 42 therein, which are of substantially the same diameter as the internal diameter of the pipes 23 and 25. The wall 38 also forms a seat around the opening 40 for a check valve 44 looselyconnected to an arm 46 which is freely pivoted on a pin 48 secured to the body 30. Within an interior compartment 49, which is generally circular in horizontal cross section, and which is formed in part by the wall 38, there is an apertured sheet metal frame 50 which supports a fine mesh cylindrical filtering screen 52. The frame and screen rest upon an annular shoulder 54 formed around the opening 42. The frame 50 and screen 52 may be inserted and removed from the body for inspection and cleaning, through an opening 56 formed in the top of the body 30, this opening being normally closed by a cap 58 secured to the body 30 by a plurality of cap screws 60. A suitable seal is effected by a torroidal gasket 64 made of a suitable oil resistant, synthetic, rubber-like material. A drain plug 66 is threaded in the body beneath the strainer and carries a permanent magnet 68 to collect any metallic particles from the oil which passes it.

The elevator is started on its upward travel by causing operationv of the pump, whereupon the oil will be withdrawn from the reservoir 10 through the screen 12 and pumpedpast the check valve 18 and pipe 23 into the compartment 49. Because the check valve 44 operates freely, nearly all of the oil will flow around the screen 52 and past the check valve 44, through cock 34 and pipe 25, and into the lower end of the jack cylinder, thus raising the jack 26 and its load 28. During the elevation of the lift, the valve 20 is closed.

After the jack has been elevated to the desired extent, the pump is stopped. When the jack is to be lowered, the control valve 22 is opened, either by direct or remote control, and the weight of the jack, together with its platform and load, if any, causes the oil to flow in a reverse direction through the assembly 22 and valve 20 to the reservoir. When the flow of oil through the assembly 22 is in reverse direction, the check valve 44 is closed and the oil necessarily flows through opening 42 into the inside of the strainer 52, and hence through the pipe 23 to the control valve 20. All of the oil which reaches the control valve is thoroughly screened by the strainer 52 so that foreign particles Will not reach the control valve to interfere with its proper operation.

At periodic intervals, especially shortly after the apparatus has been placed in operation, the shutoff cock 34 should be closed and the screen 52 and its frame 50 removed for inspection and cleaning, and the plug 68 removed and cleaned of any adhering particles.

It will therefore be clear that all of the oil which flows from the jack through the control valve is thoroughly strained by the fine mesh screen 52 so that the possibility of failure of the latter to operate properly is greatly reduced. On the other hand, any foreign material collected by the strainer is not forced back into the jack cylinder 24 because of the adequate bypass around the strainer formed by the compartment 49 and by virtue of the fact that the check valve 44 operates very freely. In many installations the distance between the control valve and the elevator is substantial, so that the use of my invention results in a saving of pipe, because if the strainer were connected at the inlet of the control valve, an additional pipe connection between the elevator cylinder and the control unit would be required.

While I have shown and described a preferred embodiment of my invention, it will be apparent that numerous variations and modifications thereof may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

I. In a hydraulic system having a means forming a conduit in which during normal operation of the system hydraulic strained fluid at times flows in one direction and at other times unstrained fluid flows in the opposite direction, means forming part of the conduit and providing two paths for the flow of the hydraulic fluid, each path having a cross sectional area substantially equal to check valve in one of the paths opening in a direction to permit flow of"thestrained fluid and closed when the --unstrained-"fluid-flows through the conduit and a--strainer in the other path, whereby the strainer is eifective to remove particles from only the flow of the unstrained zz-fluid; thefistrained': fluid flowingi freely throughlntherpath wwhich includes the check valve.

2 2..A: :combined: strainers and check valve. assembly. for hydraulicfiflu'id operated. apparatus and -.through -which :l-fluid-cisi adapted tOY'fiON in .two directions; comprising a ;-='generally':'hollow body having .two pipe connection. open- 1,; ings,: an 1 internal wall dividing the interior ofthe :body IEiIltOlifiESt andw-second:compartments-with one of. said openings communicatingwith said first compartment and the e-secondx of .said openings communicating=with said nsecond compartment, .apair of ports in said wall'through :zwhich fluid-:may flow; from one. compartment-into .the =:'other,-. a screen over-tone of-v said ports so that; all of the I'fluid1-:flowing Tthrough saidsone portmust flow through -rsaid--screennandsbe'zstrained thereby; and a freely oper- :-.able normally/closed check valve closing said. other port and openable by fluid flowing out of said-first. compartwment through-said other port and into said second comnpartment and closed by fluid flowingin a second direc- ;tion' from said second compartment and into said first z-rcompartmentywhereby all fluid flowing in said second di-rectiori and into said second compartment passes a'through said screen and is strained thereby.

3.. A combined-strainer. and check valve assembly for v-hydr-aulic fluid operated apparatus and'through which fluid-is adapted to flowin two directions, comprising a generally hollow body. having two'pipe connection open- ;.ings,.an internal wall-dividing the interior of the body into" first and second. compartments with one of said operable normally closed-check valve. closing said other port. and openableby fluidw-flowing in a :fiISi-e direction out of said first compartment through said other port and' intosaid second compartment .andr' closed by fluid flowing in a second direction from. said second compartment and into 'said""first"compartment; whereby all fluid flowing in said second direction and into said second compartment passes through said screen and is strained "thereby.

References Cited in the file of this patent UNITED STATES *PATENTS Number Name Date 493,378 Gibson Mar..14,, .1.893 1,062,793 Pendleton May..27, 1913 1,780,723 -Short --Nov. 4, ...1930 1,903,774 -Burr ell Apr. 18,1933

1 FOREIGN PATENTS Number Country Date 313,155 .G-reatiBritain May. 15,..1929 

